Actually ... we need more details of the call rather than loosing the numbers ... like miss call or answered and duration.
The data is available in the phone logs and maybe it should be extracted from there as a separate report ... in addition to the standard way of reporting.
Dear customers,
KidLogger PRO agent may be also connected to StaffCounter server.
It records not only number and duration of the call, but sound from the microphone.
Sometimes, it is possible to hear both voices.
for more information:
http://kidlogger.net/kidlogger-android-pro.html